title: X-ray scattering studies of structural phase transitions in pyrochlore Cd2Nb2O7.
abstract: Structural phase transitions in pyrochlore Cd2Nb2O7 were studied by means of single crystal x-ray scattering. On cooling below the ferroelastic transition at T1 = 204 K, the cubic Bragg peaks broaden in a manner consistent with weak orthorhombic distortion. The distortion evolves rather smoothly through the ferroelectric transition at T2 = 196 K, which explains the absence of sharp anomalies in the heat capacity and dielectric constant at this transition. At lower temperatures, the anomalous relaxor-like character of this compound is evident as a gradual reduction in the Bragg peak intensities, which continues down to the onset of another transition at T3 = 85 K. The studies of two Bragg peaks that are forbidden within the cubic phase reveal an interesting disparity: while the intensity for one of them increases in a classical mean-field manner below T1, the other shows unconventional behavior that is reminiscent of the pyrochlore superconductor Cd2Re2O7.
authors.affiliation: Department of Physics and Astronomy, McMaster University, Hamilton, ON, L8S 4M1, Canada. National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Tachibana
authors.forename: Katharina
authors.initials: K
authors.lastname: Fritsch
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Gaulin